Wang, H.-W., Hu, H.-X., Song, T.-M. and Chen, S.-J. 2012. Seed traits evaluation from long-term selection of kernel oil concentration in a high-oil maize population KYHO. Can. J. Plant Sci. 92: 857-866. A high-oil maize population, KYHO, was developed over 10 generations by selective breeding for increased kernel oil content (KOC). The objectives of this study were to evaluate kernel oil selection effects, and measure the trait changes and genetic variance in the embryo and endosperm. Oil, protein, and starch content in the embryo and endosperm were estimated by near-infrared reflectance spectroscopy (NIRS). Mass and volume of embryo and endosperm were measured. Selective breeding increased embryo oil content (EMOC) and endosperm oil content (ENOC), especially EMOC, which changed from 315.62 g kg^-1 C0 to 592.54 g kg^-1 C10, resulting in an increase in total embryo and endosperm oil content (EEOC) from 43.32 g kg^-1 C0 to 139.95 g kg^-1 C10. With selection for increase in EEOC, embryo protein content (EMPC) decreased slightly; however, endosperm protein content (ENPC) and total protein content (EEPC) increased significantly. Embryo and endosperm starch content (EMSC and ENSC) and total starch content (EESC) all decreased substantially with selection. One hundred embryo mass (EMM) was not notably changed with selection, but 100 embryo volume (EMV) increased significantly. Mass and volume of endosperm (ENM and ENV) and total mass and volume of embryo and endosperm (EEM and EEV) all decreased significantly with selection, possibly due to markedly decreased starch content. Linear regression analysis indicated with each 1 g kg^-1 EEOC increase, EMOC, ENOC, ENPC, EEPC, EMM, and EMV increased 2.74 g kg^-1, 0.16 g kg^-1, 0.38 g kg^-1, 0.36 g kg^-1, 0.06 g, and 0.20 mL, respectively, and EMPC, EMSC, ENSC, EESC, EEM, ENM, EEV, and ENV decreased 0.04 g kg^-1, 1.48 g kg^-1, 0.60 g kg^-1, 1.09 g kg^-1, 1.26 g, 1.32 g, 0.97 g, and 1.17 mL, rspectively.